1. Field of the Invention
The present invention relates to an electrophotographic photoconductor and a photoconductive composition for use in the electrophotographic photoconductor. This photoconductive composition is also useful as a photoconductive material for solar batteries, photosensors, and optical switching elements.
2. Discussion of Background
Recent development of information processing systems utilizing electrophotography is remarkable. In particular, a photoprinter which converts information to be recorded into digital signals and optically records the information is excellent in the printing quality and operational reliability. This digital recording technology is applied not only to such a photoprinter, but also to ordinary copying machines, so that a so-called digital copying machine has been developed.
A copying machine which employs the conventional analog copying technology, as well as this digital recording technology, can be provided with various information processing functions, so that it is expected that a demand for such a copying machine will be increased.
At present, semiconductor diodes (LD) and light emitting diodes (LED), which are small sized and inexpensive and have high operational reliability, are in general use as light sources for the optical printer. However, the wavelength of the light emitted from LED now in general use is 660 nm, while the wavelength range of the light emitted from LD is in a near infrared region, so that the development of an electrophotographic photoconductor having sensitivities in the range from a visible region to a near infrared region is desired.
The photosensitive wavelength range of an electrophotographic photoconductor is substantially determined by the photosensitive wavelength range of a charge generating material (CGM) employed in the electrophotographic photoconductor, so that varieties of charge generating materials have been developed. However, a single charge generating material (CGM) having a high photosensitivity in a broad wavelength range from visible through near infrared has not yet been developed.
Under such circumstances, various trials have been made for development of a photoconductor with such a broad photosensitive range by mixing a charge generating material having high photosensitivity to visible light (i.e., short wavelength CGM) and a charge generating material having high photosensitivity to near infrared light (i.e., long wavelength CGM).
For example, the following have been proposed: an electrophotographic printing plate having photosensitivities to white light, gas laser, and the light emitted from LED, prepared by mixing (a) a trisazo pigment, (b) at least one pigment selected from the group consisting of a perylene pigment and an anthanthrone pigments and (c) an electron-donating material (Japanese Laid-Open Patent Application 3-146957); an electrophotographic photoconductor having photosensitivities to white light and infrared laser, prepared by use of a disazo pigment and oxotitanium phthalocyanine (Japanese Laid-Open Patent Application 3-196049); and a photoconductor having photosensitivities to light from a visible region through an infrared region, which comprises a charge generating layer comprising a mixed pigment, and a binder agent which is composed of trigonal system selenium particles and phthalocyanine particles mixed in a styrene-butadiene copolymer (Japanese Laid-Open Patent Application 3-225346).
The above-mentioned photoconductors, however, have the shortcomings that the charging properties thereof are caused to deteriorate when exposed to ozone or NOx gases which are generated in a charger of a copying machine or a printer.